Drilling machines have been used for boring holes in the ground for many years and are used in a wide variety of applications, including boring horizontally for installing underground utilities. The basic components of a typical horizontal drilling machine include a rotational drive assembly, a longitudinal driver, a rod transferring apparatus, and a vice assembly. Each of these basic components has typically been independently controlled by dedicated controls located at an operator's station.
A conventional drilling process involves rotating a drill string (i.e., a string of interconnected pipes or rods) with the rotational drive assembly while simultaneously propelling it longitudinally. The rotational drive assembly is typically threaded into the top of the drill string, and is thus capable of rotating the entire drill string. A drilling bit is typically mounted on the opposite, bottom end of the drill string. The thrust for propelling the drill string longitudinally is provided by the longitudinal driver which typically includes an elongated guide or track on which the rotational drive assembly is slidably mounted. This longitudinal drive mechanism is capable of longitudinally propelling the drill string to advance the drill string and extend the length of the bored hole. The process of drilling a hole, longer than the length of one rod, involves the following basic steps:    1) transferring a rod from storage to a position in alignment with the rotational drive assembly;    2) attaching the top end of the rod to the rotational drive assembly and the bottom end of the rod to the drill string or drill bit, thus making the rod a part of the drill string;    3) rotating the drill string with the rotational drive assembly while advancing the rotational drive assembly forwardly along the track to propel the drill string into the ground until the rotational drive assembly is at the end of the track;    4) holding the drill string with the vice assembly while the rotational drive assembly is reversed to detach from the drill string;    5) propelling the rotational drive assembly rearwardly along the track in preparation for inserting another rod; and    6) repeating the above process thereby extending the length of the drill string and the bored hole.
As indicated above, a common purpose for drilling a bore along a predetermined path is for the installation of utilities such as cable or pipe. After the bore has been drilled, the utilities are installed within the bore by attaching the desired utility to the bottom end of the drill string and pulling the utility back through the bore. Frequently, a back reaming process is used to enlarge the bore as the utility is pulled back through the bore. During the pullback process, the above steps are basically reversed to remove rods from the drill string and to insert the removed rods back in to storage.